Invasive Species Spotlight – Elongate Hemlock Scale

Name: Elongate Hemlock Scale (Fiorinia externa Ferris)

Origin: Native to China and Japan and was first observed in New York City in 1905. It is believed that it was unintentionally introduced from Japan.

NYS Presence: Elongate hemlock scale (EHS) is present throughout the state, with the highest density within a 185 mile radius of New York City.

Identification: EHS is an armored insect most commonly found on the underside of hemlock needles. They show up as small (1.5-2 mm) and flat brown or white patches that hide the female and male insects, respectively. Underneath the brown scale, you may find the tiny yellow eggs.

Kristopher Abell, University of Massachusetts, Bugwood.org
Female EHS, look for small eggs, accessed from Kristopher Abell, University of Massachusetts, Bugwood.org

Life Cycle: “Crawlers” hatch from eggs under the female scale and emerge in the spring and summer. At this point they are mobile and can crawl to a new needle or be transported by wind or birds. Once they find a suitable site for feeding, they burrow under the waxy cuticle of the needle for protection, and insert their feeding tube into the mesophyll cells of the needle, just under the epidermis or surface layer of cells on the needs. The females will never leave this site as they go through their three stages of development. The males, however, will emerge from their five stages of development as winged adults. They will fly to a mature female, mate, and die without ever feeding. EHS overwinters either as fertilized females or eggs (typically 16-20 are laid). (Jill Sidebottom, Elongate Hemlock Scale, ncsu.edu).

Damage Pennsylvania Department of Conservation and Natural Resources -ugwood.org
EHS damage, photo accessed from Pennsylvania Department of Conservation and Natural Resources – Forestry , Bugwood.org

As EHS feeds on the hemlock needs they remove the plant’s nutrients, the needles take on a yellow color as they dry out and drop, leading to branch dieback and ultimately death in as little as ten years.

Control: One option of control is to remove highly infested trees. EHS can also be controlled chemically. The two most consistent chemical controls for EHS are Safari (a neonicotinoid) and Talus (an insect growth regulator). Safari is also used to control hemlock wooly adelgid, another invasive pest from Japan that often appears alongside EHS as white wooly ovisacs on the underside of hemlock needles. EHS can also be treated with biological agents, such as the parasitic wasp Encarsia citrina, and predatory beetles like the twice-stabbed ladybird beetle, Chilocorus stigma and Microweisea misella (Mark S. McClure, The Connecticut Agricultural Experiment Station). These biological controls have provided inconsistent results and are also susceptible to pesticides, so pesticide should be applied with that in mind. To report sightings of EHS in New York State Parks, visit  iMap Invasives or for other questions regarding invasives, email the Invasive Species Management Team at invasives@parks.ny.gov

The Invasive Species Management Team consists of Strike Teams and Forest Health Specialists. Strike Teams travel statewide for various invasive plant removal projects. Forest Health Specialists travel statewide as well, monitoring trees for the presence of forest pests like EHS and HWA among others.

Post by Sarantia Mitsinikos, Invasive Species Project Steward

Featured image photo by Irene Brenner

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